The present invention relates to bumpers having a hitch adapted to haul a trailer or the like, and also to bumpers having energy absorbers adapted to mount accessories and form steps.
Rear bumpers of vehicles, especially utility vehicles and trucks, are often adapted with hitches to haul trailers. The hitch-supporting structure is often incorporated into the bumper in order to reduce components and to provide a more compact arrangement. With stamped bumpers, the hitch-supporting structure is simply stamped into the bumper beam as the bumper components are formed and auxiliary reinforcements are added. However, it is more problematic with rollformed tubular bumper beams, since rollforming operations are not typically set up to incorporate stamping operations. Further, tubular beams often use higher-strength materials, such that it is not as easy to form a hitch-supporting structure in a tubular beam. Also, hitch-supporting structures require that the side walls of the material be cut and shaped, at a time when it is difficult to support an inside of the tube. This makes it difficult if not impossible to accurately shape the wall as desired.
Sometimes, the towing strength of the hitch-supporting structure is more limited than desired. In particular, class II hitches must be able to support a tongue weight of 350 lbs., and must be able to tow a weight of 3500 lbs.; while class III hitches must be able to support a tongue weight of 500 lbs., and must be able to tow a weight of 5,000 lbs. The difference between the two hitch classes is considerable, and the structure necessary to pass the tougher class III standard is not easily achieved without significant cost, weight, and vehicle-built-in structure.
In addition to the above, it is desirable to reduce the number of components required to mount accessories such as tail lights, turn signal lights, license plate illuminating lights, and the like, onto bumper systems. Further, it is desirable to form features integrally into the bumper system, such as steps and other mounting features, without the need for separate bracketry and extra parts attached to the beam. However, it is difficult to form features integrally into a roll-formed beam during a rollforming process, since the process of rollforming produces a continuous cross section, while mounting features require some discontinuity, such as holes, hooks, and/or secondary mechanical deforming operations. Historically, energy absorbers made of plastic are not suitable for mounting, since the plastic is chosen to optimize energy absorption with a consistent energy-absorbing collapse (as opposed to bearing weight). Only recently have plastic materials been developed that are suitable to do both. Another problem is related to gross vehicle weight. Typically, bumper reinforcement beams are extended past the vehicle frame mounts to form bumper steps, with the beam providing the structure necessary to support the weight of a person stepping on the bumper ends. However, this results in considerable additional weight added to the bumper system, since reinforcement beams are metal and tend to be heavy. Thus, any distance that the beam extends laterally beyond the vehicle frame mounts adds undesirably to gross vehicle weight.
Accordingly, a bumper system is desired solving the aforementioned problems and having the aforementioned advantages.